The classic prior art approach to designing wheeled carts and vehicles that operate on soft surfaces such as sand or mud is to use larger wheels or more wheels at the side of the cart. For the purposes of this application, the wheeled device is referred to as a cart, since that is the most ideal use of the invention. However, the inventive concept is equally applicable to any type of vehicle and the word cart should be understood to include all types of wheeled devices.
The prior art use of larger wheels requires that the wheels be located at the perimeter of the cart so that the load bearing surface of the cart can be kept reasonably close to the ground where it is accessible to convenient loading and unloading of whatever cargo is being carried on the cart. The larger, or more numerous, perimeter located wheels do allow travel over softer and more irregular surfaces, but it is still possible to encounter ground so soft and so irregular that the load bearing surface between the wheels will come to rest on the ground, stranding the wheels in the air without traction. This is especially true on sand surfaces, such as at the beach, where the wheels can continuously dig down until the load bearing surface bottoms out on the sand. Additional wheels, or more wheels, just adds to the expense and makes the cart more clumsy without really solving the problem. The present invention contemplates an entirely new approach that provides a cart that is impossible to bottom out in soft and irregular surfaces, while still being very low in cost, size, and weight.